From what I have heard, mitochondrial disease is generally thought to be there from birth, hence the roadblock to the idea it can happen later in life, i.e. ME CFS
I know a 12 year old girl who was diagnosed with a genetic Mitochondria disease by Duke University at age TWO. She was born with it and it comes from the mother's side. So, she does not have CFIDS but does have MY CFIDS symptoms, most of them anyway. Poor kid. Her parents have done much of what the CFIDS people have done vis-a-vis meds and vitamins. She has NO immune system at all and her babyhood vaccines did not show up at all when they tested her. They gave her an ultra expensive med to bump up her immune system and then were going to give her all her babyhood vaccines again, but sadly the expensive immune med did not work.
What did come to mind is that maybe we too have some sort of genetic fault in our mitochondria and then the rest of the triggers set in and we wind up with CFIDS. Dr. Kerr did find 88 genes associated with CFIDS and one (or maybe more) of those genes was a downregulated Mitochondria gene. Hope I didn't mess this one up - so double check what I have noted here.